Environmental Health Center
It's not so much rising temperature and rising seas that scientists in the Pacific Northwest think of when they consider the potential impacts of global climate change in their region. Instead, it's what Seattle Post-Intelligencer environmental reporter Rob Taylor called "rain with bad timing."
The scientific community uses somewhat more esoteric language in describing the potential consequences of global warming. And with due scientific caution they generally caveat their evaluations more as "scenarios" than as outright predictions or projections. And they frequently pose as many questions as they attempt to answer.
Take, for instance, the remarks of Amy Snover with the University of Washington's Joint Institute for the Study of Atmosphere and Ocean, a co-author a 1997 paper on impacts of global warming in the Pacific Northwest. Based on a climate-modeling scenario provided by a major general circulation computer modeling (GCM) center, the Max Planck Institute fur Meteorologie in Hamburg, Germany, Snover reaches the following conclusion:
"It is becoming evident that climate change will be manifested most directly in the Pacific Northwest through changes to the region's hydrologic cycle. Changes in water availability and in the timing of supply will impact all aspects of the region: forests, aquatic ecosystems, coastal activities, agriculture, human health, energy supply, and urban centers."
Snover's colleague, Dennis Lettenmaier, shares that perspective, summarizing as follows: Pacific Northwest "hydrologic response to climate is strongly linked to a) winter-dominant precipitation, and b) role of snow."
"All scenarios would result in decreases in hydropower reliability," Lettenmaier says. That is an especially important consideration in the upper Northwest, where hydro in the mid-1990s provided about 60 percent of the electrical power.
Marine ecosystems and fisheries are central to the economy and environment of the Northwest. When the University of Washington School of Fisheries' R.C. Francis evaluates effects of climate change on the region's fisheries, he points to four factors as being particularly important: "timing, distribution, intensity, and persistence." Those, rather than direct heating of the ocean, should command close attention in evaluating potential climate change impacts in the Pacific Northwest, Francis writes.
Consisting for our purposes here of the states of Washington, Oregon, and Idaho, the Pacific Northwest is home to more than 9,700,000 people - about 5.5 million in Washington's 68,192 square miles, 3.2 million in Oregon's 96,981 square miles, and 1.1 million in Idaho's 83,557 square miles.
Capturing the Northwest's diversity in a few easy-to-swallow soundbites isn't easy…and probably not accurate. The rugged Pacific Ocean and inner marine coasts of Oregon and Washington contrast with the interior wheatlands, sagebrush desert, and high desert and lava fields. Three major vegetation types - forest, shrub-steppe, and alpine - characterize the region. But "climatic variation across the Pacific Northwest gives rise to many different patterns," some 80 attendees at a July 1997 climate change workshop were reminded. "Forests, for example, range from coastal Sitka spruce to interior ponderosa pine communities. The degree of complexity found in the Pacific Northwest is highly unique in the United States."
Fairly dry and warm summers and cool wet winters characterize the region, but such generalizations can mislead. "Average annual precipitation ranges widely, both across the region and locally," participants at the Office of Science and Technology Policy\U.S. Global Change Research Program July 1997 meeting were reminded. Example: Washington's Snoqualmie Pass averages 91 inches of precipitation annually, while Yakima, Washington, just 70 miles distant, averages 7.9 inches per year.
Population and employment have been increasing appreciably in the Pacific Northwest since the mid-1990s. Washington, Oregon and Idaho all rank among the top 10 states nationally in non-farm job growth in 1995-1996. The three states' combined population increase of 1.8 percent during 1994 and 1995 was about double the national average. Most of the employment growth came in the fields of service and trade and not in the forestry and timber sectors so much a part of the region's past.
Along with most of the other western states, population increases in Oregon, Washington, and Idaho are expected to significantly outpace most of the rest of the U.S. between 2000 and 2025. The U.S. Census Bureau projects a 33.3 percent population increase in Washington over that period, with Oregon and Idaho populations projected to increase by 28 and 29.3 percent respectively.
The Columbia River Basin, the fourth largest in the United States, is the region's dominant water resources system, transcending both national and international boundaries and draining parts of British Columbia and seven states. The basin has more than 250 reservoirs and 100 hydroelectric projects and little room for future development." The region's rapid growth and development, along with changing approaches and priorities for allocating water resources, are widely seen as stressing the system. "There is simply not enough water flowing in the system to meet all the demands," say the three public sector agencies overseeing the river.
Following the approach taken by Snover and her colleagues at the University of Washington, one can consider eight different features of the Pacific Northwest in light of potential climate change:
Scientists at the University of Washington anticipate the region could see more precipitation in winter and less in summer. They expect warmer winter temperatures to bring more rain and less snow, a consequent decrease in snowpack accumulation, and likely more snowmelt earlier in the year - all of which would lead to less water storage. Water supply challenges may be particularly evident in east-of-Cascades rivers, particularly in summer months.
West of the Cascades, where Tacoma gets its water supply for instance, they can foresee a doubling of instances in which river systems fail to meet instream flow requirements necessary for fisheries protection. In addition, they anticipate that climate change will result in a "considerable increase in flood frequency."
Looking specifically at the Columbia River Basin, the scientists write that hydrologic changes will be "extremely sensitive to the spatial distribution of future changes in precipitation," and those do not occur uniformly over the basin. Energy production, fish protection, and irrigation water supply could be affected by projected changes in runoff timing and in average streamflow. Additional power sources would likely be needed to supplement hydropower.
In terms of fisheries protection, they point to a potential decline from 85 percent to 74 percent reliability in meeting minimum flow requirements by 2020. By 2050 the reliability falls to 74 percent, they say. "These flow requirements are difficult to meet today, due to the limited storage available to support them, and become more difficult to meet" under the Max Planck scenario.
Along with water quantity concerns, the University of Washington scientists point also to water quality issues. "Dilution of wastes, from point and nonpoint sources, depends on river flows," they write. Irrigation runoff, the largest nonpoint source of pollutants into the Columbia River, "peaks during summer months when river flows are lowest. The potential for higher dissolved oxygen concentrations in some lakes and tributaries could harm some fish populations."
"Forests are most strongly linked to climate during regeneration, and through climate's impact on disturbances," the scientists say. "It is through these links that the impacts of future climate change will be manifested most clearly."
Temperature and moisture will directly affect photosynthesis, respiration "and other important physiological processes," the authors say, along with forest productivity generally. "As temperature increases, the moisture available for plant growth will decline, even with no change in precipitation." That situation would be exacerbated by the modeled decline in summer precipitation.
The frequency and intensity of "disturbance regimes" - wildfires and pest outbreaks - would increase under the modeled scenario. "Regions of increased summer drought will experience increased risk of fire, perhaps extending hazard into areas not now affected, particularly where forests are dead or already stressed by drought or pests," they write. Some insects and pests in a warmer climate would complete more generations per year.
Freshwater fisheries in small lakes and rivers likely would be most susceptible to climate change, followed by estuarine fisheries subjected to sea level rise or declining river flows. Salmon migration and spawning could be hurt, and altered sedimentation patterns could harm fish habitat and lead to declines in the survival rates for egg-smolt. Increased freshwater temperature likely would pose problems for fish reproductive potential and growth, and freshwater species confronting higher temperatures likely would migrate northward.
"Anthropogenic processes such as coastline armoring, wetland filling, logging, agriculture, dredging, exotic species introductions and other disturbances have had a far greater impact on the coastal zone than past climate-related impacts," the authors say. "Future climate change is unlikely to supersede these effects" but rather will pose additional stresses "to systems already under a great deal of development and population pressure."
With a higher base for storm surges and increased flooding potential, the scientists say that soil saturation resulting from the higher groundwater table could limit water runoff during flooding. Both in the Puget Sound and on Oregon's and Washington's outer coasts, they anticipate increased coastal erosion, and they see sea level rise flooding low-lying coastal areas and wetlands. "Parts of Highway 101 in Oregon are likely to be flooded and may need to be moved with a 30 cm (one foot) rise in sea level."
As coastal residents "harden" their shorelines - that is, build more bulkheads and other structures - issues will arise concerning habitat loss, loss of wetlands and riparian vegetation, and loss of spawning habitats. Other potential impacts include salt water intrusion into freshwater aquifers, malfunctioning of coastal storm drains, changed sewage treatment plant outfall hydraulics, and increased contamination of groundwater.
Irrigation needs may increase with higher temperatures, a potential problem in particular in the Snake and Yakima River basins, where water allocations already are approaching limits. Increased temperatures could extend the ranges of some agricultural pests or speed-up their life cycles, and livestock production could be harmed by reduced grazing and pasture productivity. In certain cases, livestock vector-borne diseases could be exacerbated, the scientists think.
The University of Washington researchers note that hydropower production "is highly dependent on climate," and they say reliability of meeting energy production goals "would decrease significantly" under the scenario in the Max Planck Institute modeling. Additional power sources likely would be needed.
OSTP/USGCRP Regional Workshop on The Impacts Of Global Climate Change on The Pacific Northwest: Final Report, Amy Snover, Edward Miles, and Blair Henry JISAO Climate Impacts Group, University of Washington, Seattle, Washington July 31, 1997 http://tao.atmos.washington.edu/PNWimpacts/final/finalcontents.html
The Regional Impacts of Climate Change; An Assessment of Vulnerability. R.T. Watson, M.C. Zinyowera, and R.H. Moss, eds. A special Report of IPCC Working Group II, published for the Intergovernmental Panel on Climate Change, Cambridge University Press, New York, 1998.
U.S. Environmental Protection Agency, "STATE IMPACTS: Oregon," EPA Global Warming Site, http://www.epa.gov/globalwarming/impacts/stateimp/oregon/index.aspx, Publication EPA 236-F-98-007u, Updated January 14, 2000, accessed Feb. 2, 2000.
U.S. Environmental Protection Agency, "STATE IMPACTS: Washington," EPA Global Warming Site, http://www.epa.gov/globalwarming/impacts/stateimp/washington/index.aspx, publication EPA 230-F-97-008uu, Updated January 14, 2000, accessed Feb. 2, 2000.
U.S. Environmental Protection Agency, "STATE IMPACTS: Idaho," EPA Global Warming Site, http://www.epa.gov/globalwarming/impacts/stateimp/idaho/index.aspx, Publication EPA 236-F-98-007f, Updated January 14, 2000, accessed
| June 23, 2000 | | Disclaimer/Policy |
